The cleaning process of textiles and clothes generally refers to the removal of contaminants therefrom, and can largely be divided into two categories. One is a general water-cleaning process comprising dispersing a surfactant in water to increase an alkalinity degree of water and remove contaminants from textiles and clothes, then rinsing the textiles and clothes, followed by wringing and drying. The other is a dry-cleaning process used to clean delicate fabrics (e.g., natural protein fabrics such as wool and silk, artificial silk, and acetate fiber) that cannot withstand the alkaline cleaning conditions as mentioned above, and the long term rough and tumble of a washing machine which can cause significant wear and tear, stress and distortion, causing the fibers to damage, break, shrink, and become irreversibly matted. The dry-cleaning uses solvents, for example, petroleum-based solvents, chlorinated solvents, glycol ester-based solvents, cyclic silicone- or silicone-based solvents, fluorinated solvents, and terpene oil such as limonene so as to dissolve and remove oil-based contaminants, and the used solvents are removed from the fabrics by a physical method and volatilized by drying.
The water-cleaning process (general cleaning method), which uses a general detergent and plenty of water, is effective in removing water-based contaminants, but is limited in the removal of oil-based contaminants. Also, due to the alkaline cleaning conditions and the long term rough and tumble of a washing machine, significant wear and tear, stress and distortion cause the fibers to damage, break, shrink, and become irreversibly matted.
Recently, in order to prevent the damage and distortion of clothes caused by the use of alkaline detergents, neutral liquid detergents are commercially available. However, since the neutral liquid detergents require mixing with water before use, the damage and distortion of clothes caused by the water cannot be prevented.
Meanwhile, to prevent the disadvantages of water cleaning such as the damage and distortion of clothes caused by the water cleaning process above, dry cleaning is often used. However, this dry cleaning process is effective in removing oil-based contaminants but is limited in the removal of water based contaminants. Also, since dry-cleaning mostly uses a chemical solvent that is harmful to the human body and environment, it should be carried out in a closed washing system that is very expensive and requires complicated maintenance.
In dry-cleaning, different kinds of soaps obtained by mixing various ionic surfactants, e.g., nonionic, anionic, cationic or amphoteric surfactants with trace amounts of water have been used as a component for improving such a limitation in the removal of water-based contaminants. Such soap is added to a solvent for dry-cleaning in trace amounts for laundry. However, as the solvent for dry-cleaning has low affinity with water, there is a limitation in the amount of soap to be used, and therefore, it is still difficult to remove water-based contaminants.
Various solvents for dry-cleaning have the following characteristics. Chlorinated solvents such as perchloroethylene (PERC) and trichloroethylene are most widely used in dry-cleaning and are advantageous in terms of being incombustible and inducing little to no damage to fabrics. However, the chlorinated solvents cause air pollution and are considered as being non-biodegradable and carcinogenic.
For this reason, petroleum-based solvents having about 5 to 13 carbon atoms have been recently used, especially a mixture of straight, branched and cyclic hydrocarbons has been used instead of the chlorinated solvents. However, the petroleum-based solvents may cause fires and explosions as well as environmental pollution as a volatile organic compound (VOC) generating ozone. Also, a microbial contamination may occur in the petroleum-based solvents themselves. In addition, stoddard solvent, which is assumed to be a representative hydrocarbon used in dry cleaning, has been known to induce carcinogenesis through inhalation.
In order to solve such problems, various researches have been conducted to develop a solvent for dry-cleaning which is safe on the human body and more environment-friendly.
For example, U.S. Pat. No. 7,087,094 discloses the use of dipropylene glycol n-propyl ether, and U.S. Pat. No. 7,144,850 discloses the use of dipropylene dimethyl ether, as an ethylene glycol ether-based solvent. These ethylene glycol ether-based solvents are relatively harmless to the human body and environment and can contain water in a certain amount. However, a lot of energy and time are needed to dry textiles or clothes due to their high volatilization temperature.
Also, U.S. Pat. Nos. 4,685,930; 6,042,617; and 6,063,135 use a cyclic silicon-based solvent as an environment-friendly solvent. However, such a cyclic silicon is also carcinogenic, has a very low affinity with water, and exhibits very poor removal of liphophilic contaminants.